Rolling bearing unit

ABSTRACT

A rolling bearing unit includes a resin-made cover attached at the opening of the vehicle inward side edge section of an outer ring. The cover includes a cylindrical portion which is fitted into the inner peripheral surface of the opening of the vehicle inward side edge section of the outer ring. A metal ring body is provided at the inner peripheral surface of the cylindrical portion.

BACKGROUND OF THE INVENTION

The present invention relates to a rolling bearing unit for rotatablysupporting the wheels of an automobile or the like on a suspensionsystem. More specifically, the invention relates to a rolling bearingunit equipped with a cover at an opening on an outer ring edge.

As disclosed in Japanese Laid-Open Patent Application Publication No.10-19912, the rolling bearing unit is structured so that a cover made ofresin is attached to the outer ring edge section opening to make itdifficult for muddy water or the like to enter the bearing via theopening. The cover comprises a circular plate portion for covering theouter ring edge section opening and a cylindrical portion which isfitted into the inner peripheral surface of the opening with clearance.In such a cover, when the cylindrical portion is fitted into the innerperipheral surface of the outer ring edge section opening, thecylindrical portion is deformed into a narrow end and a gap occursbetween the inner peripheral surface of the opening and the outerperipheral surface of the cylindrical portion, so the function ofpreventing muddy water from entering the bearing may be degraded.

BRIEF SUMMARY OF THE INVENTION

The present invention is a rolling bearing unit comprising a cover atthe outer ring edge section opening, wherein the cover comprises acircular plate portion for covering the outer ring edge section openingand a resin-made cylindrical portion which is fitted into the innerperipheral surface of the outer ring edge opening, and a metal ring bodyis provided at the inner peripheral surface of the cylindrical portion.

According to the present invention, when the resin-made cylindricalportion of the cover is fitted into the inner peripheral surface of theouter ring edge section opening, deformation force acting radiallyinward on the cylindrical portion is stopped by the ring body,end-narrowing deformation of the cylindrical portion is suppressed, andthe cylindrical portion closely contacts the inner peripheral surface ofthe outer ring edge section opening. As a result, attachment strength ofthe cover to the outer ring edge section opening is increased and it ispossible to effectively prevent moisture from entering the bearing.

As a preferred embodiment of the present invention, if theaxial-direction length of the ring body is made shorter than the innerfitting length with respect to the inner peripheral surface of the outerring edge opening on the cover cylindrical portion, the ring bodystrength for stopping deformation force acting radially inward on thecylindrical portion increases, and end-narrowing deformation of thecylindrical portion is suppressed more effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

Accompanying the specification are figures which assist in illustratingthe embodiments of the invention, in which:

FIG. 1 is a cross-sectional view of a rolling bearing unit according toa preferred embodiment of the present invention;

FIG. 2 is a view showing a principal portion of FIG. 1;

FIG. 3 is a cross-sectional view of a principal portion of a rollingbearing unit according to another configuration of the presentinvention;

FIG. 4 is a cross-sectional view of a principal portion of a rollingbearing unit according to still another configuration of the presentinvention;

FIG. 5 is a cross-sectional view of a principal portion of a rollingbearing unit according to still another configuration of the presentinvention; and

FIG. 6 is a cross-sectional view of a principal portion of a rollingbearing unit according to still another configuration of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, referring to the drawings, description will be made of arolling bearing unit for vehicles according to a preferred embodiment ofthe present invention.

FIG. 1 is a cross-sectional view of the same rolling bearing unit. InFIG. 1 the left side represents the side toward the vehicle outside andthe right side represents the side toward the vehicle inside. An outerring 1 is made of metal such as high-carbon steel meeting JIS S55C orbearing steel meeting JIS SUJ-2, and is a fixed ring fixed to the bodyof a vehicle such as an automobile.

The outer ring 1 comprises a flange portion 14 for vehicle body fixingfor supporting the outer ring 1 on a suspension system (not shown) atthe outer peripheral surface roughly in the center thereof in the axialdirection. The ring 1 also comprises outer ring raceways 12 and 13 onits inner peripheral surface on the vehicle outward side and the vehicleinward side respectively.

A hub spindle 2 constitutes a ring that rotates with respect to theouter ring 1. The hub spindle 2 comprises a flange portion 15 for wheelfixing at the outer peripheral surface on the vehicle outward side. Thehub spindle 2 also comprises an inner ring raceway 16 opposite the outerring raceway 12 at an outer peripheral surface more inward than theflange portion 15.

An inner ring 3 is outwardly fitted to the outer peripheral surface of asmall-diameter cylindrical portion 2 a on the side toward the vehicleinward side of the hub spindle 2 and is capable of rotating unitarilywith the hub spindle 2. The inner ring 3 thus constitutes a ring thatrotates together with the hub spindle 2 with respect to the outer ring1.

The inner ring 3 comprises an inner ring raceway 17 opposite the outerring raceway 13 on the outer peripheral surface. The inner ring 3 isprevented from slipping out by a bent edge section 2 b on the side ofthe hub spindle 2 toward the vehicle inward side, and is pre-pressuredthereby.

A plurality of balls 4 and 5 are rotatably held between the outer ringraceways 12 and 13 and the inner ring raceways 16 and 17 by cages 6 and7 respectively. A seal 8 is interposed between the inner peripheralsurface of the vehicle outward edge section of the outer ring 1 and theouter peripheral surface of the hub spindle 2.

In order to protect the inside of the bearing from external muddy wateror the like in conjunction with the seal 8, the rolling bearing unitcomprises a resin-made cover 11. The cover 11 is cylindrical and has abottom, at an opening 1 b of an edge section 1 a on the side of theouter ring 1 toward the vehicle inward side.

The cover 11 comprises a circular plate portion 20 which covers theopening 1 b of the vehicle inward side edge section 1 a of the outerring 1. A cylindrical portion 21 of the cover 11 is inwardlypress-fitted to the inner peripheral surface of the opening 1 b. Aflange portion 22 of the cover is provided at the periphery of thecircular plate portion 20 and restricts the inner fitting depth of thecylindrical portion 21 with respect to the inner peripheral surface ofthe opening 1 b of the outer ring 1.

Preferably, most of the entire cover 11 is formed of a resin. A metalring body 25 is integrally provided at the inner peripheral surface ofthe cylindrical portion 21. Preferably, the material of the ring body 25is a cold rolled steel sheet meeting such standards as JIS SPCC.Furthermore, it is not necessary to form the entire cover 11 of resin.For example, only the cylindrical portion 21 may be formed of resin.

Referring to FIG. 2, the structure of the cover 11 shall be described inmore detail. Illustrated is the positional relationship in the axialdirection between the vehicle inward side edge 1 a of the outer ring 1and the vehicle inner side edge 2 b of the hub spindle 2. As a result ofthis relationship, the axial-direction length B of the inner peripheralsurface of the cylindrical portion 21 of the cover 11 is made longerthan the axial-direction length A of the outer peripheral surfacethereof.

Therefore, when the cylindrical portion 21 of the cover 11 is pressfitted into the inner peripheral surface of the opening 1 b of the edgesection 1 a of the outer ring 1 on the vehicle inward side, the tip sideof the cylindrical portion 21 in the press fitting direction contractsand is easily deformed into a cone shape. This is because thecylindrical portion 21 is made of resin and the outer ring 1 is metal.

In order to prevent such deformation, vehicle outward side end face 25 aof the ring body 25 is positioned so as to be in the same plane radiallywith the vehicle outward side end face 21 a of the cylindrical portion21. Furthermore, the end face 25 b on the vehicle inward side ispositioned more to the vehicle outside than the vehicle inward side rootportion 21 b of the outer peripheral surface of the cylindrical portion21.

When the cylindrical portion 21 of the cover 11 is fitted into the outerring 1, the ring body 25 stops force acting radially inward on thecylindrical portion 21 and prevents the cylindrical portion 21 frombeing deformed into a cone shape. In particular, the vehicle inward sideedge section 25 b on the ring body 25 is positioned more to the vehicleoutward side than the vehicle inward side root portion 21 b of thecylindrical portion 21. As a result, the deformation of the tip side ofthe cylindrical portion 21 of the cover 11 into a cone shape is morereliably prevented when the cylindrical portion 21 of the cover 11 isfitted into the outer ring 1, and this is preferred.

Accordingly, as the outer peripheral surface of the cylindrical portion21 of the cover 11 makes close contact with the inner peripheral surfaceof the opening 1 b of the vehicle inward side edge section 1 a of theouter ring 1, the attachment strength of the cover 11 to the outer ring1 is increased. It is thus difficult for moisture to enter inside thebearing, thereby improving hermetically sealing of the bearing interior.

If the ring body 25 is not provided, when the temperature of the rollingbearing unit rises a gap may occur between the opening 1 b of the outerring 1 and the cylindrical portion 21 of the cover 11. This is becauseof the difference in thermal expansion between the outer ring 1 and thecover 11, i.e., the coefficient of linear expansion of the outer ring 1is greater than the coefficient of linear expansion of the cover 11.

In this embodiment, the ring body 25 thermally expands in a mannersimilar to the outer ring, i.e., the coefficient of linear expansion ofthe outer ring 1 is equal to the coefficient of linear expansion of thecylindrical portion 21. As illustrated, the ring body 25 is provided atthe inner peripheral surface of the cylindrical portion 21. Accordingly,the diameter of the cylindrical portion 21 expands by the thermalexpansion of the ring body 25 and the outer peripheral surface of thecylindrical portion 21 makes close contact with the inner peripheralsurface of the outer ring 1, thereby preventing occurrence of the gap.

The material of the cover 11 is preferably a resin which has acoefficient of linear expansion approximately that of the material ofthe outer ring 1. Examples are polyamide (PA), polyphenylene sulfide(PPS), and polybutylene terephthalate (PBT). If a resin whosecoefficient of linear expansion is approximately that of the material ofthe outer ring 1 is selected as the cover 11 material, the followingoccurs. As the temperature rises, the cover 11 also expands to the sameextent as the outer ring 1, and it is possible to ensure such a fittingforce that the cover 11 cannot not be pulled out of the outer ring 1.When the temperature drops, the cover 11 also shrinks to the same extentas the shrinkage of the outer ring 1, thereby preventing cracking of thecover 11.

As shown in FIG. 3, it is also possible to have a structure thatincreases the rigidity of the cylindrical portion 21 by insert-formingthe ring body 25 at the cylindrical portion 21 of the cover 11 and bybending the tip side of the ring body 25 radially outward.

In an alternative embodiment, as shown in FIG. 4, the ring body 25 mayalso be insert-formed at the cylindrical portion 21 so as to cross thewhole inner peripheral surface of the cylindrical portion 21 of thecover 11. More specifically, the resin cover 11 attached to the opening1 b of the vehicle inward side edge section 1 a of the outer ring 1comprises the cylindrical portion 21. The cylindrical portion 21 isfitted into the inner peripheral surface of the opening 1 b of thevehicle inward side edge section 1 a of the outer ring 1. The cover 11also includes the flange portion 22 which contacts an end face 1 c ofthe vehicle inner side edge section 1 a of the outer ring 1. The metalring body 25 is provided at the inner peripheral surface of thecylindrical portion 21. The ring body 25 is extended from an innerperipheral surface area S1 of the cylindrical portion 21 to an innerperipheral surface area S2 of the flange portion 22.

According to the configuration described above, the cover 11 is attachedto the outer ring 1 so that the flange portion 22 contacts the end face1 c of the vehicle inward side edge section 1 a of the outer ring 1 fromthe axial direction. In this case, the cylindrical portion 21 of thecover 11 is slightly bent due to its elasticity while being inserted.However, the ring body 25 is fixed to the area from the inner peripheralsurface area S1 of the cylindrical portion 21 of the cover 11 to theinner peripheral surface area S2 of the flange portion 22. Accordingly,some of the elastic bending portion of the cylindrical portion 21 issupported by the rigidity of the ring body 25.

When the wheel rotates due to vehicle use, the temperature of the outerring 1 rises and the heat is transmitted to the cylindrical portion 21.When the vehicle is stopped, the temperature of the outer ring 1 fallsand this temperature change is transmitted to the cover 11. Here, if thecylindrical portion 21 is formed only of resin, there will bedifficulties in adapting to temperature changes. This is because of theresin coefficient of linear expansion, so there is the danger that thecover 11 may fall off the outer ring 1.

In view of the danger of the cover falling off, the ring body 25 couldbe provided at the inner peripheral surface region of the cylindricalportion 21 of the cover 11. This would make it difficult for the coverto fall off the outer ring even when thermal shock from heating andcooling occurs. Moreover, merely providing the ring body 25 at the innerperipheral surface area of the cylindrical portion 21, depending on thetype of resin, results in insufficient adaptation to temperaturechanges. In this case, there is the danger that the cylindrical portion21 will deform, reducing the contact area with the inner peripheralsurface of the outer ring 1 and degrading pullout force.

In view of the potential for deformation, in this embodiment, the ringbody 25 extends from the inner diameter side area S1 of the cylindricalportion 21 to the inner diameter side area S2 of the flange portion 22.Accordingly, the starting point for bending of the cylindrical portion21 is separated from the outer ring 1 (which is a heat source), and theamount of metal at the portion where bending occurs is increased. As aresult, so the resin bending amount is suppressed.

Therefore, even when a thermal shock occurs as in temperature increaseand decrease of the outer ring 1, because of the metal, bending of thecylindrical portion 21 is kept to a minimum. Moreover, the necessarycontact area between the outer peripheral surface of the cylindricalportion 21 and the inner peripheral surface of the outer ring 1 issecured. Therefore the required pullout force is secured, therebyeffectively preventing the cover 11 from falling off the outer ring 1.

The above structure provides the following benefit. For example, aknurled groove or other groove may form at the inner peripheral surfaceof the vehicle inward side edge section of the outer ring 1. The groovemay engage the outer peripheral surface of the cylindrical portion 21.However, if the cover 11 is incorporated in the outer ring 1, part ofthe cylindrical portion 21 resiliently enters the grooved portion. As aresult, the cover 11 is effectively prevented from being pulled out ofthe outer ring 1.

An opening may be provided for fitting a rotation detection device onthe cover 11, and the rotation detection device may be fitted in theopening. This rotation detection device detects the rotational speed orthe like of the wheel in order to control a vehicle anti-lock brakesystem (ABS) or a traction control system (TCS). It is advantageous touse the cover 11 as a cover equipped with such a rotation detectiondevice. This is because the cover 11 is unlikely to fall off the outerring 1 even when a thermal shock such as heating and cooling occurs.

As shown in FIG. 5, the axial length B of the inner peripheral surfaceof the cylindrical portion 21 of the cover 11 is set approximately thesame as the axial length A of the outer peripheral surface.Alternatively, as shown in FIG. 6, the axial length B of the innerperipheral surface of the cylindrical portion 21 of the cover 11 is setshorter than the axial length A of the outer peripheral surface. Ineither case, the ring body 25 can be disposed with respect to thecylindrical portion 21 in a manner similar to that of FIG. 2 or FIG. 3.In both configurations, screwing a nut in the hub spindle 2 preventspullout of the inner ring 3 from the hub spindle 2.

The present invention is applicable to a rolling bearing unit forrotatably supporting wheels of an automobile or the like on a suspensionsystem.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not as restrictive. The scope of the invention is, therefore,indicated by the appended claims and their combination in whole or inpart rather than by the foregoing description. All changes that comewithin the meaning and range of equivalency of the claims are to beembraced within their scope.

1. A rolling bearing unit comprising: an outer ring including an edgesection opening, said opening including an inner peripheral surface; acover connecting to said opening; said cover comprising: a circularplate portion covering said opening; and a cylindrical portion joined tosaid circular plate and including an cylinder inner peripheral surfaceand an opposing cylinder outer peripheral surface, said cylindricalportion being resin, said cylindrical portion fitting into and havingsaid cylinder outer peripheral surface contacting said inner peripheralsurface of said opening to retain said cover in said opening; and a ringbody provided in contact with said cylinder inner peripheral surface ofsaid cylindrical portion at a position opposing a portion of saidcylinder outer peripheral surface contacting said inner peripheralsurface of said opening, said ring body being metal and providingsupport to said cylindrical portion to effect press fitting of saidcover to said opening.
 2. The rolling bearing unit of claim 1, whereinsaid ring body is axially shorter than said cylinder inner peripheralsurface of said cylindrical portion.
 3. The rolling bearing unit ofclaim 1, wherein said ring body and said cylindrical portion of saidcover each includes an end face, and said end faces are coplanar.
 4. Therolling bearing unit of claim 1, wherein said ring body is integratedwith said cylindrical portion by insert forming.
 5. The rolling bearingunit according to claim 4, wherein said ring body includes an end face,and said end face is disposed radially outward.
 6. A rolling bearingunit comprising: an outer ring including an axial inward side, saidaxial inward side of said outer ring including an edge section opening,said opening including an inner peripheral surface; a cover connectingto said opening; and said cover comprising: a circular plate portioncovering said opening; a cylindrical portion press fitting into saidinner peripheral surface of said opening, said cylindrical portionhaving a periphery and a cylinder inner peripheral surface and anopposing cylinder outer peripheral surface in press fit contact withsaid opening, said cylindrical portion being resin; a flange portionprovided at said periphery of said cylindrical portion, said flangeportion defining a depth by which said cylindrical portion extends intosaid outer ring opening; and a metal ring body provided on and incontact with said cylinder inner peripheral surface of said cylindricalportion at a position opposing a portion of said cylinder outerperipheral surface contacting said inner peripheral surface of saidopening and providing support to said cylindrical portion to effectpress fitting of said cover to said opening.
 7. The rolling bearing unitaccording to claim 6, wherein: said cylinder inner peripheral surface ofsaid cylindrical portion is axially longer than said cylinder outerperipheral surface thereof; said ring body and said cylindrical portioneach include an end face, said end faces being coplanar; and saidcylindrical outer peripheral surface is axially longer than said ring.8. The rolling bearing unit of claim 7, wherein: said outer ring, saidring body and said cylindrical portion each have coefficients of linearexpansion; and said coefficients of linear expansion for both said outerring and said ring body are greater than said coefficient of linerexpansion of said cylindrical portion.
 9. The rolling bearing unitaccording to claim 7, wherein said cover is a resin, and said cover hasa coefficient of linear expansion essentially equal to said coefficientof linear expansion of said outer ring.
 10. A rolling bearing unitcomprising: an outer ring including outer and inner peripheral surfaces,said outer ring including axially outward and axially inward edges, saidouter peripheral surface comprising a flange portion and said innerperipheral surface comprising first and second outer ring raceways; ahub spindle including an axial outward side and an axial inward side,each respectively having an axial outward edge and an axial inward edge;said axial outward side of said hub spindle including an outerperipheral surface, said outer peripheral surface of said hub spindleincluding a flange portion; said hub spindle having an inner ringraceway opposing said first outer ring raceway, both said inner ringraceway of said spindle and said first outer ring raceway being disposedaxially between said axial inner edge of said outer ring and said flangeof said hub spindle; and said hub spindle including a small diametercylindrical portion disposed axially between said axial inner edge ofsaid hub spindle and said inner ring raceway of said hub spindle; saidbearing unit further comprising an inner ring disposed against saidsmall diameter cylindrical portion of said hub spindle, said inner ringincluding an outer peripheral surface, said outer peripheral surface ofsaid inner ring comprising an inner ring raceway, said inner ringraceway opposing said second outer ring raceway of said outer ring; aplurality of rolling members disposed between said respective outer ringand inner ring raceways; a seal disposed between first and secondsurfaces, said first surface being defined by said inner peripheralsurface of said outer ring, adjacent to said axially outward edge ofsaid outer ring, and said second surface being defined by said outerperipheral surface of said hub spindle; and said axially inward edge ofsaid outer ring defining an inward edge of an opening, said openingincluding an inner peripheral surface; said unit further comprising acover connecting to said opening, said cover being resin; said covercomprising: a circular plate portion for covering said opening; acylindrical portion joined to said circular plate and including acylinder inner peripheral surface and an opposing cylinder outerperipheral surface press fitting to said inner peripheral surface ofsaid opening; and a flange portion disposed on said cylinder outerperipheral surface of said cylindrical portion, said flange portiondefining a depth by which said cylindrical portion extends into saidopening of said outer ring; and a ring body provided on and in contactwith said cylinder inner peripheral surface of said cylindrical portionat a position opposing a portion of said cylinder outer peripheralsurface contacting said inner peripheral surface of said opening, saidring body being provided on said cylinder inner peripheral surface byinsert forming, said ring body being metal.
 11. The rolling bearing unitaccording to claim 10, wherein: said ring body and said cylindricalportion of said cover each include an axially outward side end face, andsaid axially outward side end faces are coplanar; and said cylinderouter peripheral surface of said cylindrical portion is axially longerthan said ring body.
 12. The rolling bearing unit of claim 10, whereinsaid ring body end face is disposed radially outward.
 13. The rollingbearing unit of claim 10, wherein: said flange portion of said coverincludes an inner peripheral surface, and said inner peripheral surfaceaxially extends inward of said inner peripheral surface of saidcylindrical portion; and said ring body extends along said innerperipheral surfaces of both said cylindrical portion of said cover andsaid flange portion of said cover.